Author Topic: Inductor adapter for a digital multimeter.  (Read 3996 times)

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Offline merishi

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Inductor adapter for a digital multimeter.
« on: January 07, 2012, 02:07:38 am »
Have any one around here tried building or using any inductor adapter for a multimeter ? Is it worth trying or is this concept just a rubbish.  I have seen some adapters on the webpages  and thought of giving it a try. But wanted to hear from you guys whether  it is worth giving a try or its just useless.

http://www.electro-tech-online.com/content/464-inductance-measuring-adapter-multimeter.html

I just wanted a simple decent DIY inductor meter because I couldnt find one on the market in my country...
 

Offline eternal_noob

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Re: Inductor adapter for a digital multimeter.
« Reply #1 on: January 07, 2012, 06:54:31 am »
I won't say it's useless, but there are too many components that can affect the measurement result IMHO. It will need frequent calibration I'm afraid.
There is a better method and that is to mimic many of those LC meters out there already, by using the Shifted Frequency of an oscillator, but this require that you have a frequency counter of some sort available. A counter on a multimeter will work just fine since it is the difference in frequency we are after, not an accurate one-spot frequency. We then manually calculate the C or L based on the difference. This method is accurate within 1 to 3 percent as long as the Q of the capacitor or inductor is reasonably good.
It is also easy to inject a current through the measured inductor on different frequencies to see whats happening with all those ferrite cores scrounged over the years. Way more flexible!
I have created a simple javascript calculator to use with this circuit but the coding is absolutely horrible and will make me stand out as a complete fool here on this forum  :-[ But, I will give it to you if you PM me. I can also help out with a calibrated inductor and/or capacitor (L1, C1) if you need to.



« Last Edit: January 07, 2012, 07:14:08 am by eternal_noob »
 


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